Manufacture of bulked yarns



United States Patent 3,137,991 MANUFACTURE OF BULKED YS Kenneth D.Fairley, Newport, England, assignor to British Nylon Spinners Limited,Pontypool, England No Drawing. Filed Aug. 5, 1963, Ser. No. 300,042Claims priority, application Great Britain Aug. 14-, 1962 14 Claims.(Cl. 57-160) This invention is concerned with improvements in orrelating to processes for the manufacture of bulked yarns.

It has long been the intent of those skilled in the textile art todevise processes for imparting to the so called man-made fibres andfilaments, hereinafter referred as yarns, some of the more desirableproperties of the naturally occurring fibers such as wool. Particularattention has been paid to the manufacture of man-made yarns having thecovering power, handle and insulation properties of wool. In recentyears processes for achieving this end have been primarily intended forapplication to the wholly synthetic yarns such as those based on thepolyamide, polyester or acrylic classes of polymers, and have been thesubject of numerous patent applications.

The majority of the aforementioned processes have been concerned withthe crimping of continuous filament yarns in order to increase theirbulk and thus display the desired qualities while retaining the moredesirable properties of the synthetic yarn, for example high strength(tenacity) and excellent abrasion resistance.

Staplised Wholly synthetic yarns also have some of the desired qualitiesbut have only a relatively low tenacity. In order to retain theproperties of the staple yarns but obtain an improved tenacity, staplefibers have been wound as a sheath around a core of a continuousfilament yarn so that the continuous filament yarn is the load bearingcomponent of the combined sheath and core yarn.

It is with processes for obtaining bulked yarns of this latter type thatthe present invention is particularly concerned.

The plying or twisting together of two or more continuous filament yarnswhich have been drawn to different amounts, so that on redrawing one endbreaks to give a yarn composed of a continuous filament core with astaple fibre sheath, in which the loose ends of the staple fibers standout from the yarn, is well known-in the art. However this processsulfers from the disadvantages that any crimp in either of these yarnsis largely removed during the redrawing operation so that the combinedyarn has only a low bulk, also considerable lapping of the broken endsaround the draw-roll occurs. We have now found that the expensiveprocess of twisting the two components of different orientations beforedrawing can be replaced by false-twisting two components of differentspun orientation together at drawing. Thus when two polyhexamethyleneadipamide yarns of different spun orientation are heated and then havefalse-twist inserted between the snubber pin and draw roll, the yarn iscrimped at drawing, and simultaneously the yarn having the highest spunorientaiton breaks into staple fibres, having a minimum length of about8 inches, in the highly twisted drawing zone which traps the brokenfilament ends. In the subsequent untwisting zone the crimp in the yarnfrom the twisting and heat setting process makes the broken ends curlinto the yarn, entangling with the continuous filaments, to form astretch type bulked yarn with a sheath of long crimped staple fiberssurrounding a continuous filament core. We have also discovered that theprocess for producing this type of sheath and cpre yarn need not belimited to the use of yarns having differing orientations, but may beachieved by the use of two or more yarns having differing physicalcharacteristics "ice which result in the said yarns having diiferentdrawing performances i.e. different extensions to break. Extension tobreak is defined as being the amount by which a yarn may be elongatedbefore it breaks.

Thus considering two polyamide yarns which are to be subjected to theprocess of false twisting at drawing as described hereinbefore, althoughthis invention is not to be taken as being, in any way limited topolyamide yarns, the physical properties and therefore the drawingperformance of one of these yarns may be arranged to differ from theother in, for example, one of the following ways. An additive e.g.alkathene may be included in the polymer prior to spinning to yield arelatively weak yarn of poor drawing performance, the yarn may be spununder conditions which result in the filaments having denier variationsor different spun orientations or it may be subjected to randomquenching after spinning, e.g. by spraying water onto the yarn while inthe conditioner tube, so that a highly spherulitic yarn is obtained, oragain random fusion of the filaments, may be induced at spinning. Inthese latter instances the yarns would all have relatively poor drawingperformances. Alternatively the yarn may be abraded or otherwisephysically or chemically damaged at spinning or in some subsequentoperation.

It is not necessary that the yarns to be used in this process be of thesame type, for example one may be a polyester and the other a polyamideor a polyhydrocarbon and a polyamide, or again a polyester and apolyhydrocarbon, provided that they have different drawing performances.Also one yarn may be non-drawable and the other drawable, for examplerayon and a polyamide, or fully drawn and undrawn polyamides.

According to one aspect therefore, the present invention provides aprocess for the manufacture of a bulked yarn comprising a crimpedcontinuous filament core surrounded by a sheath of staple fibres,wherein two or more yarns, at least one of which is thermoplastic,having different extensions to break are heated and the combined yarnssimultaneously false-twisted and drawn, the amount of drawing beingsufficient to cause the yarn having the lowest extension to break tobreak into staple length fibres, which fibres form a sheath around theremaining unbroken crimped yarn or yarns which thereby form a crimpedcontinuous filament core, the ends of the said staple fibers becomingentangled with the filaments of the core.

The term yarn includes bundles of filamentary materials, threads andother plied structures.

We have further found that a tension-stable bulked yarn can be obtainedby further processing of the sheath and core yarn described above. Inthis context a tension stable yarn is defined as a bulked yarncontaining a continuous filament core which does not suffer a loss inbulkiness when subjected to a lengthwise tension.

By passing the drawn yarn obtained by the process as previouslydescribedherein through a second heated zone under controlled tension, the crimpin the continuous filament core is removed while the crimp in the stablefibre sheath is further developed, to give a tension-stable yarn havingan uncrimped continuous filament core and a sheath of crimped staplefibres.

From another aspect therefore this invention further provides a processfor the manufacture of a tension-stable yarn comprising a substantiallycrimp free continuous filament core surrounded by a sheath of crimpedstaple fibres, wherein a yarn obtained according to the processdescribed hereinbefore is subsequently heated under controlled tensionto remove substantially all of the crimp from the continuous filamentcore and further develop the crimp in the staple fibre sheath.

The invention includes the bulked and tension stable yarns produced asdescribed above and textile articles woven or knitted therefrom.

A particularly suitable method for inserting false-twist in a yarn whichmay be employed in the process of this invention is that known as theflange false-twist process and described in the specification forLetters Patent No. 890,053. In the use of this method in the process ofthis invention yarns having different spun-orientations are fed fromfeed rolls around a heated snubbing pin to a draw roll provided with aflange, the combined yarn is caused to rub against the said flange,which rapidly rotates the said yarn and imparts a false-twist thereto,so that the yarn is drawn while in an intensely false-twisted condition.The broken filament ends, resulting from the yarn having the lowestextension to break breaking during drawing, are locked in the yarn andthus prevented from lapping around the draw roll, a condition frequentlyencountered when ends break at drawing.

The processes of this invention will now be more fully described in thefollowing examples which are intended to be merely illustrative and notlimitative of the invention.

In these examples the method for inserting false-twist while drawing isthat previously described herein in which a 3.820 inch diameter drawrollis fitted with a 5.75 inch diameter flange of Shore Hardness 80. Thesnubber pin, offset 1.5 inches from the flange, is electrically heatedand has an acid-etched chromium plated surface maintained at 185 C. toheat-set the false-twist at drawing.

Example 1 Undrawn yarns of polyhexamethylene adipamide are employed inthis example as follows:

(a) High spun-orientation component-20 filament yarn having a denier of181 and a spun birefringence of 0.021.

(b) Low spun-orientation component-25 filament yarn having a denier of404 and a spun birefringence of 0.0075.

The above yarns are drawn together over the flange at a speed of Sf.p.m. to a drawn ratio of 3.65 to give a combined 45 filament yarn oftotal denier 160 in which the yarn having the higher spun-orientation isbroken into long lenth staple fibers. The combined yarn thereforecomprises a core of crimped 25 filament 4 denier continuous filamentyarn surrounded by a sheath of crimped 3 denier per filament staple yarnhaving a staple length of several feet.

A weft knitted fabric made from this yarn had a pleasing appearance anda warm soft handle.

Woven fabrics containing the bulked yarn of this invention as a Weftacross a 60 denier polyhexamethylene adipamide warp in a plain weavecount 100 x 69 or a four end sateen weave 100 x 90 have many small loopsand filament ends protruding from the surface, and possess an attractivedry handle.

Example 2 A 20 filament polyhexamethylene adipamide yarn in which ten ofthe filaments have a different spun orientation from the remainder isobtained in the following manner. The molten polyamide is extruded intofilaments through 20 orifices contained in a single spinneret plate andsolidified by a transverse blast of air in the conventional manner. Tenof the filaments thus obtained are taken and caused to pass around twospaced ceramic pins such that the filaments make two turns through 90and then recombined with the remaining filaments. The combined filamentsare next passed through a steam conditioning tube and wound up onto apackage in the usual manner. The effect of passing ten of the filamentsaround ceramic pins is to increase the tension in those filaments andhence cause them to be drawn to a greater extent 4 and thus have ahigher spun orientation than the re maining filaments.

This yarn is processed in the manner described for the combined yarns inExample 1 to give a bulked yarn comprising a core of 10 crimpedcontinuous filaments surrounded by a sheath of long length staplefibres.

Example 3 Undrawn polyhexamethylene adipamide yarns used in this exampleare:

(a) High spun-orientation component-13 filament yarn having a denier of119 and a spun birefringence of 0.019.

(b) Low spun-orientation component-13 filament yarn having a denier of152 and a spun birefringence of 0.011.

These yarns are drawn together over the flange at a speed of 450 f.p.m.to a draw ratio of 3.66 to give a bulked core and sheath yarn having atotal denier of 80. After leaving the draw roll the yarn is wrapped 1%times around a 1 inch diameter metal pin maintained at 205 C. beforebeing wound up. The tension in the yarn between the pin and the wind upis maintained substantially constant at 0.15 gm./denier. The resultantbulked yarn is tension stable with small loops of crimped fibressurrounding a substantially uncn'mped continuous filament core.

A fabric in which the tension stable yarn of Example 3 is woven as weftacross a 60 denier polyhexamethylene yarn as warp in a plain weave count100 x has a drier handle and less lustrous appearance than either afabric woven with a corresponding continuous filament unbulked weft, ora continuous filament bulked weft containing no broken filamentsproduced by drawing together two undrawn yarns of the same spunorientation, under the conditions detailed in this example for theproduction of the tension stable yarn.

The presence of broken filaments in this tension stable yam results in amarked increase in the specific volume (gm/cc.) of the yarn comparedwith a continuous filament 80 denier 26 filament unbulked yarn or acontinuous filament 80 denier 26 filament bulk yarn produced under thesame conditions as the tension stable yarn but without broken ends i.e.by drawing together two yarns of the same spun orientation, as shown inthe table below:

Yarn: Specific volume, g./cc. Tension stable yarn of Example 3 2.0Similar yarn without broken filaments 1.5 Continuous filament unbulkedyarn 1.19

It can be seen that breaking some of the filaments into long staplelengths increases the specific volume of the yarn, making a greatercontribution to the total than falsetwisting at drawing.

The specific volume of the yarn is measured by winding onto a containerof volume 10.30 cc. at a tension of 7 g., the weight of yarn required tofill this volume is a measure of the specific volume of the yarn whichis expressed in g./cc.

Although the above examples have been described with particularreference to polyhexamethylene adipamide yarns, it is to be understoodthat the invention may be effectively applied to all polyamide and otherthermoplastic yarns such as those based on polyesters orpolyhydrocarbons.

What I claim is:

l. A process for the manufacture of a bulked yarn comprising a core ofcrimped continuous filaments surrounded by a sheath of staple lengthfibres, wherein two or more yarns, at least one of which isthermoplastic, having different extensions to break are combined, andare false twisted and drawn while in a heated condition to cause theyarn having the lowest extension to break to break into crimped staplelength fibres, which fibres form a sheath around the remaining unbrokencrimped filaments which thereby form a core of crimped continuousfilaments, the ends of the staple fibres entangling with the continuousfilament core.

2. A process according to claim 1 wherein the yarns are initially formedfrom the same starting materials but have difierent orientations.

3. A process according to claim 2 wherein the yarns are initially formedfrom the same starting materials but have different spun orientations.

4. A process according to claim 3 wherein the yarns are formed as asingle yarn from polyhexamethylene adipamide which is formed intofilaments by melt extrusion through a spinneret and a proportion of thefilaments so formed is subjected to a greater tension than the remainingfilaments before Winding up to impart thereto a higher spun orientation.

5. A process acording to claim 4 wherein the tension is applied to thefilaments by causing them to pass over two or more ceramic pins aftersolidification and before passage through a steam conditioning tube.

6. A process according to claim 1 wherein one yarn is treated by achemical or physical process to weaken it with respect to the remainingyarns.

7. A process according to claim 6 wherein the yarn is formed by meltspinning and is weakened by random quenching of the melt spun filaments.

8. A process according to claim 2 wherein one yarn is a fully drawn highmolecular weight synthetic polymer yarn.

9. A process according to claim 8 wherein the polymer ispolyhexamethylene adipamide.

10. A process according to claim 1 wherein the staple fibres formed bythe process have a minimum length of 8 inches.

11. A process for the manufacture of a tension staple bulked yarncomprising a substantially crimp free continuous filament coresurrounded by a sheath of crimped staple fibres wherein the yarn ofclaim 1 is heated under a controlled tension to remove substantially allof the crimp from the continuous filament core and further de velop thecrimp in the staple fibre sheath.

12. A process according to claim 11 wherein the fibres in the crimpedstaple fibre sheath have an uncrimped length of at least 8 inches.

13. A process according to claim 11 wherein the yarns are composed ofpolyamides.

14. A process according to claim 13 wherein the yarns arepolyhexamethylene adipamide yarns.

References Cited in the file of this patent UNITED STATES PATENTS2,904,953 Groombridge et a1 Sept. 22, 1959 3,061,998 Bloch Nov. 6, 1962FOREIGN PATENTS 1,158,282 France Jan. 20, 1958 1,251,346 France Dec. 12,1960 850,059 Great Britain Sept. 28, 1960

1. A PROCESS FOR THE MANUFACTURE OF A BULKED YARN COMPRISING A CORE OFCRIMPED CONTINUOUS FILAMENTS SURROUNDED BY A SHEATH OF STAPLE LENGTHFIBRES, WHEREIN TWO OR MORE YARNS, AT LEASST ONE OF WHICH ISTHERMOPLASTIC, HAVING DIFFERENT EXTENSIONS TO BREAK ARE COMBINED, ANDARE FALSE TWISTED AND DRAWN WHILE IN A HEATED CONDIDTION TO CAUSE THEYARN HAVING THE LOWEST EXTENSION TO BREAK TO BREAK INTO CRIMPED STAPLELENGTH FIBRES, WHICH FIBRES FORM A SHEATH AROUND THE REMAINING UNBROKENCRIMPED FILAMENTS WHICH THEREBY FORM A CORE OF CRIMPED CONTINUOUSFILAMENTS, THE ENDS OF THE STAPLE FIBRES ENTANGLING WITH THE CONTINUOUSFILAMENT CORE.